Huge bacteria that eat viruses close the gap between life and non life, Scientists have discovered hundreds of unusually large bacteria-killing viruses, characteristics often associated with living organisms and which blur the line between living germs and the virus engine.

These phages are short for bacteriophages, which are called because they “eat” bacteria of the size and complexity considered to be the hallmark of life, carry many of the genes normally found in bacteria, and use these genes to fight their host bacteria. Huge bacteria that eat viruses close the gap between life and non life.

The researchers discovered this giant phage by searching for a large database of DNA they had produced from nearly 30 different terrestrial environments, from the gut of premature babies and pregnant women to Tibetan hot springs, South African bioreactors, hospital rooms, and oceans. , Lakes and more. deep underground.

In total, they have identified 351 different giant phages whose genomes are four or larger than the average genome of viruses that spit with unicellular bacteria.

Among them are the largest bacteriophages found so far: its genome, 735,000 base pairs, is almost 15 times larger than the average phage.

Ironically, in the DNA this giant phage likes, they are part of the CRISPR system that bacteria use to fight viruses. It is likely that after this phase of injecting their DNA into bacteria, the CRISPR virus system will spread the CRISPR system to the host bacteria, perhaps mainly to target other viruses. Huge bacteria that eat viruses close the gap between life and non life.

“It is very interesting how this phage changes this system, which we think is bacterial or ancient, to our advantage against our competitors to wage a war between these viruses.

One giant phage can also make a protein that resembles the Cas9 protein which is part of the revolutionary CRISPR-Cas9 tool used by UC Berkeley, Jennifer Dudna and her European counterpart Emanuel Charpentier adapted for gene editing.

The team calls this small protein CasØ because the Greek letter Ø or Phi is traditionally used for bacteriophages.

Many of the genes found are unknown, have no suspected function and can be a source of new proteins for industrial, medical or agricultural applications.

This new finding not only provides new ideas about the ongoing war between phages and bacteria, but also has an impact on human disease.

Viruses generally carry genes between cells, including genes, which provide antibiotic resistance.

And because phages can be found wherever bacteria and archeas live, including human intestinal microbiomes, they can send harmful genes to bacteria that colonize humans.

Some diseases are caused indirectly by phages, because phages move around genes involved in pathogenesis and antibiotic resistance. And the bigger the genome, the greater the ability to move around this type of gene, and the more likely it is that you can send unwanted bacterial genes to the human microbiome. Huge bacteria that eat viruses close the gap between life and non life.

For more than 15 years, Banfield has been studying the diversity of bacteria, Archea, which according to researchers, is a cousin of bacteria and phages of interest in various environments on the planet.

Researchers have found that many new microbes have a very small genome that seems insufficient to lead an independent life. Instead, they seem to depend on other bacteria and archaea to survive.

The team identified 351 phage genomes with a length of more than 200 kilobases, four times the length of the phage gene an average of 50 kilobytes (kb). They were able to determine the exact phage genome length 175; the other can be much larger than 200 kb. One complete genome, 735,000 base pairs in length, is the largest phage genome known today.

While most genes encode unknown proteins in this giant phage, researchers have been able to identify genes that encode proteins that are important for machines called ribosomes that convert messenger RNA into proteins.

Researchers have found many RNA transfer genes that transfer amino acids to ribosomes to be incorporated into new proteins. Protein genes that contain and regulate mRNA; Protein genes are involved in translation, and even fragments of the ribosome itself.

Usually life is different from non-life through ribosomes and the ability to translate. This is one of the most important features that separates viruses and bacteria, non-life and life, according to the researchers. Some large phages have many of these machine translations, so they blur the sentence a little

Some giant phages also have alternative genetic codes, and nucleic acid triplets encode certain amino acids that can confuse the bacterial ribosomes that translate RNA.

Some giant phages also have a CRISPR arrangement, an area of ​​the bacterial genome that stores viral DNA fragments for future reference, so that bacteria can recognize the returning phage and mobilize their Cas protein to target and target them. cut off.

The high-level conclusion is that phages with large genomes are quite prominent in Earth’s ecosystems, they are not ecosystem features, the researchers said.

And phages with large genomes are interconnected, which means that they are an established genus with a long history of large genome sizes. The existence of large genomes is a successful existence strategy and a strategy that we know little about.